U.S. patent application number 11/994669 was filed with the patent office on 2009-02-05 for serial signal transmission system.
Invention is credited to Koji Hoshina, Hizuru Nawata, Shintaro Soma, Yuzo Yoneyama.
Application Number | 20090036168 11/994669 |
Document ID | / |
Family ID | 37708761 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090036168 |
Kind Code |
A1 |
Nawata; Hizuru ; et
al. |
February 5, 2009 |
SERIAL SIGNAL TRANSMISSION SYSTEM
Abstract
A transmission device includes signal synthesizer 16 that
replaces the least significant bits of a plurality of transmission
and reception target data that are digital signals with bit data of
a desired control signal that is a digital signal, and serial
signal converter 17 that converts the output signal from the signal
synthesizer into a serial signal and transmits the serial signal.
On the other hand, a reception device includes parallel signal
converter 21 that converts the received serial signal into a
parallel signal to acquire transmission and reception target data,
and signal separator 23 that extracts the bit data of the control
signal from the respective least significant bits of transmission
and reception target data output by parallel signal converter
21.
Inventors: |
Nawata; Hizuru; (Tokyo,
JP) ; Soma; Shintaro; (Tokyo, JP) ; Hoshina;
Koji; (Tokyo, JP) ; Yoneyama; Yuzo; (Tokyo,
JP) |
Correspondence
Address: |
NEC CORPORATION OF AMERICA
6535 N. STATE HWY 161
IRVING
TX
75039
US
|
Family ID: |
37708761 |
Appl. No.: |
11/994669 |
Filed: |
August 1, 2006 |
PCT Filed: |
August 1, 2006 |
PCT NO: |
PCT/JP2006/315203 |
371 Date: |
January 4, 2008 |
Current U.S.
Class: |
455/561 |
Current CPC
Class: |
H04L 1/0068 20130101;
H04L 1/0079 20130101 |
Class at
Publication: |
455/561 |
International
Class: |
H04W 88/00 20090101
H04W088/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2005 |
JP |
2005-225253 |
Claims
1. A serial signal transmission system for transmitting and
receiving a serial signal in accordance with a specification for an
internal interface in a radio base station apparatus provided in a
mobile communication system, the system comprising: a transmission
device including a signal synthesizer replacing the least
significant bits of a plurality of transmission and reception
target data that are digital signals, with bit data of a desired
control signal that is a digital signal, and a serial signal
converter converting an output signal from the signal synthesizer
into a serial signal and transmitting the serial signal; and a
reception device including a parallel signal converter receiving
the serial signal and converting the received serial signal into a
parallel signal to acquire the transmission and reception target
data, and a signal separator extracting bit data of the control
signal from the respective least significant bits of the
transmission and reception target data output by the parallel
signal converter.
2. The serial signal transmission system according to claim 1,
wherein the transmission device includes a scrambler for generating
and using a pseudo random signal to scramble the control signal and
for supplying the scrambled control signal to the signal
synthesizer, and the reception device includes a descrambler using
the same pseudo random signal generated by the scrambler to
descramble the control signal extracted by the signal separator, to
reproduce the unscrambled control signal.
3. The serial signal transmission system according to claim 1,
wherein the transmission device is radio equipment specified in
CPRI that is a specification for the internal interface in the
radio base station apparatus, and the reception device is radio
equipment control specified in the CPRI.
4. The serial signal transmission system according to claim 1,
wherein the transmission device is radio equipment control
specified in CPRI that is a specification for the internal
interface in the radio base station apparatus, and the reception
device is radio equipment specified in the CPRI.
5. The serial signal transmission system according to claim 2,
wherein the transmission device is radio equipment specified in
CPRI that is a specification for the internal interface in the
radio base station apparatus, and the reception device is radio
equipment control specified in the CPRI.
6. The serial signal transmission system according to claim 2,
wherein the transmission device is radio equipment control
specified in CPRI that is a specification for the internal
interface in the radio base station apparatus, and the reception
device is radio equipment specified in the CPRI.
7. The serial signal transmission system according to claim 5,
wherein the descrambler uses a frame signal specified in the CPRI
to synchronize the pseudo random signal used for the descramble
process with the pseudo random signal used for the scramble process
by means of the scrambler.
8. The serial signal transmission system according to claim 1,
wherein the signal synthesizer replaces the least significant bits
of the transmission and reception target data with bit data of the
control signal at every predetermined period.
9. The serial signal transmission system according to claim 1,
wherein the signal synthesizer extracts the transmission and
reception target data having the largest amplitude at every
predetermined period to replace the least significant bits of the
extracted transmission and reception target data with bit data of
the control data.
10. The serial signal transmission system according to claim 6,
wherein the descrambler uses a frame signal specified in the CPRI
to synchronize the pseudo random signal used for the descramble
process with the pseudo random signal used for the scramble process
by means of the scrambler.
Description
TECHNICAL FIELD
[0001] The present invention relates to a serial signal
transmission system that is suitably used for an internal interface
in a radio base station apparatus provided in a mobile
communication system.
BACKGROUND ART
[0002] In recent years, two types of standard specifications have
been formulated for internal interfaces in radio base station
apparatuses provided in a mobile communication system. One of the
two types of standard specifications is CPRI (Common Public Radio
Interface) and the other is OBSAI (Open Base Station Architecture
Initiative). Both types of specifications have been voluntarily
formulated by the industry. Related companies have been promoting
development of apparatuses including internal interfaces conforming
to these specifications. The two types of specifications allow the
serial transfer of digitalized baseband signals between a radio
section and a baseband processing section both of which are
provided in the radio base station apparatus.
[0003] FIG. 1 shows the configuration of a radio base station
apparatus including an internal interface conforming to the
CPRI.
[0004] The radio base station apparatus shown in FIG. 1 includes
radio equipment (RE) 1 which amplifies power for radio signals and
which executes, for example, a frequency conversion between a radio
signal and a baseband signal, radio equipment control 2 (REC) which
manages radio resources and which executes modulation/demodulation
processes and the like. Radio equipment 1 and radio equipment
control 2 are connected together via an interface (CPRI Link)
conforming to the CPRI.
[0005] The CPRI defines, as interfaces for connecting radio
equipment 1 and radio equipment control 2 together, a physical
layer (Layer 1) through which digitalized baseband signals, that
are electric or optical signals, are transmitted and received, a
data link layer (Layer 2) in which flow control, management of
transmitted and received data, and the like are executed. In
accordance with the CPRI, radio equipment 1 and radio equipment
control 2 transmit and receive, to and from each other, IQ data
(User) for each user, synchronizing signals (Sync.) used to
transmit and receive digitalized baseband signals, and control and
management data (Control & Mgmt.) that allow a CPRI link to be
maintained.
[0006] To transmit and receive the IQ data (hereinafter referred to
as user data) for each user as a digitalized baseband signal, radio
equipment 1 and radio equipment control 2 form frames by
consecutively arranging user data D.sub.MSB, D.sub.2, D.sub.3, . .
. , D.sub.LSB made up of a plurality of bits (for example, 10 bits)
as shown in FIG. 2 and transmit and receive the user data frame by
frame. A frame signal (10 bits) is located at the head of each of
the frames in order to allow the boundary between the frames to be
identified.
[0007] For example, if radio equipment 1 (transmission device)
transmits transmission and reception target data (the frame) to
radio equipment control 2 (reception device), radio equipment 1
converts and transmits the frame signal shown in FIG. 2 and the
user data into respective serial signals. Radio equipment control 2
converts the serial signal transmitted by radio equipment 1 into a
parallel signal. Radio equipment control 2 further separates the
frame signal from the user data and demodulates the user data. This
also applies to the case in which radio equipment control 2
transmits frames to radio equipment 1.
[0008] In the meantime, if various pieces of information are
transmitted and received between radio equipment 1 and radio
equipment control 2, a desired control signal for independent
control may be transmitted and received and this signal is
different from the control data specified in the CPRI or the like.
To transmit and receive the desired control signal (digital
signal), the following two methods can be used in general.
(a) Besides the interface defined in the CPRI or the like in order
to allow each piece of information to be transmitted and received,
a dedicated interface is provided for transmitting and receiving
the control signal. (b) The control signal is synthesized with the
signal defined in the CPRI and transmitted and received between
radio equipment 1 and radio equipment control 2, for example, with
the frame composed of a plurality of user data.
[0009] For example, Japanese Patent Laid-Open No. 2002-351482
(hereinafter referred to as Patent Document 1), which belongs to a
technical field different from that of the present invention,
discloses a technique of replacing lower bits of a sound signal
from the transmission device with data other than sounds (text
information or the like); the reception device separates the data
other than sounds from the received sound signal.
[0010] A new interface circuit and wiring for the interface are
disadvantageously required for the method of providing the
dedicated interface for transmitting and receiving the control
signal, among the methods by which the radio equipment control and
radio equipment transmit and receive the control signal as
described above.
[0011] Furthermore, according to the method of synthesizing the
control signal during the transmission and reception between the
radio equipment control and the radio equipment, the synthesized
signal used after the synthesis needs to be transmitted at a higher
rate in order to maintain a signal bit rate used before the
synthesis. The configuration of the interface circuit also needs to
be changed so as to enable signals to be transmitted at the higher
rate. This disadvantageously results in an expensive interface
circuit.
[0012] The technique described in Patent Document 1 embeds data
other than sounds in the sound signal. This disadvantageously
limits the transmission rate of transmissible data other than the
sound signal, preventing the technique from being applied directly
to the control signal transmitted and received between the radio
equipment control and the radio equipment. For example, the
transmission rate of the sound signal is at most about 64 kbps.
Embedding the control signal in the sound signal limits the
transmission rate of the control signal to about several Kbps.
DISCLOSURE OF THE INVENTION
[0013] An object of the present invention is to provide a serial
signal transmission system of enabling a desired control signal to
be transmitted and received between a transmission device and a
reception device without the need to add an interface circuit or
wiring or to increase the transmission rate.
[0014] To accomplish this object, the present invention allows a
transmission device to replace the least significant bits of a
plurality of transmission and reception target data with bit data
of a desired control signal for transmission. On the other hand, a
reception device extracts the bit data of the control signal from
the respective least significant bits of the received transmission
and reception target data.
[0015] The serial signal transmission system in accordance with the
present invention enables the desired control signal to be
transmitted and received without the need to add an interface
circuit or an interface line or to increase the transmission rate.
This makes it possible to prevent an increase in the costs of the
transmission device and reception device provided in a radio base
station apparatus to transmit and receive serial signals.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram showing the configuration of a
radio base station apparatus including an internal interface
conforming to the CPRI;
[0017] FIG. 2 is a schematic diagram showing the configuration of
the format of conventional frames transmitted and received between
radio equipment and radio equipment control;
[0018] FIG. 3 is a block diagram showing the configuration of the
radio equipment to which a serial signal transmission system in
accordance with the present invention is applied;
[0019] FIG. 4 is a block diagram showing the configuration of the
radio equipment control to which the serial signal transmission
system in accordance with the present invention is applied; and
[0020] FIG. 5 is a schematic diagram showing the configuration of
the format of frames for use in the present invention which are
transmitted and received between the radio equipment and the radio
equipment control.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021] A serial signal transmission system in accordance with the
present invention replaces the least significant bits (LSB) of a
plurality of transmission and reception target data transmitted and
received between radio equipment and radio equipment control both
provided in a radio base station apparatus, with respective bit
data of a control signal to transmit and receive the control
signal. In this case, the LSBs of all the transmission and
reception target data need not be replaced with the control signal.
The radio equipment and the radio equipment control replace the
LSBs of the transmission and reception target data with the control
signal in accordance with a predetermined "period" or "rule".
[0022] Furthermore, the serial signal transmission system in
accordance with the present invention uses a pseudo random signal
such as a PN (Pseudo Noise) signal to scramble (encode) the control
signal, which is a digital signal, and replaces the scrambled
control signal with the LSBs of the transmission and reception
target data.
[0023] FIG. 3 is a block diagram showing the configuration of radio
equipment to which the serial signal transmission system in
accordance with the present invention is applied. FIG. 4 is a block
diagram showing the configuration of the radio equipment control to
which the serial signal transmission system in accordance with the
present invention is applied. FIG. 5 is a schematic diagram showing
the configuration of the format of frames for use in the present
invention which are transmitted and received between the radio
equipment and the radio equipment control.
[0024] As shown in FIG. 3, radio equipment includes antenna 11 that
receives a radio signal, reception amplifier 12 that amplifies the
signal received by antenna 11, frequency converter 13 that converts
the frequency (radio frequency) of the signal output by reception
amplifier 12 into the frequency of a baseband signal, AD converter
14 that converts the baseband signal (analog signal) output by
frequency converter 13 into a digital signal, scrambler 15 that
uses the pseudo random signal to scramble a desired control signal,
signal synthesizer 16 which replaces the LSBs of user data
(transmission and reception target data) in the digitalized
baseband signal with the scrambled control signal and which adds a
frame signal to the control signal to generate a frame, and serial
signal converter 17 that converts the frame generated by signal
synthesizer 16 into a serial signal.
[0025] As shown in FIG. 4, the radio equipment control includes
parallel signal converter 21 that converts the serial signal
transmitted by the radio equipment into a parallel signal to
acquire the frame signal and the user data respectively,
demodulator 22 that extracts the user data from an output signal
from parallel signal converter 21 to demodulate the user data,
signal separator 23 that separates the control signal from the
output signal from parallel signal converter 21, and descrambler 24
that descrambles the control signal separated by signal separator
23 to reproduce the original unscrambled control signal.
[0026] Now, description will be given of the operation of the radio
equipment, shown in FIG. 3, and of the radio equipment control,
shown in FIG. 4.
[0027] A radio signal received by antenna 11 has the power thereof
amplified by reception amplifier 12. The signal is then converted
into an intermediate frequency signal by frequency converter 13.
Here, it is assumed that the radio signal is converted directly
into a baseband signal that is IQ data for each user.
[0028] The baseband signal (analog signal) output by frequency
converter 13 is converted into a digital signal of k (for example,
k=8 or 10) bits by AD converter 14. As shown in FIG. 2, the
conventional serial signal transmission system adds a frame signal
to a baseband signal (user data) converted into a digital signal to
form a frame, converts the frame into a serial signal, and
transmits the serial signal to the radio equipment control.
[0029] According to the present invention, as shown in FIG. 5, the
LSBs (D.sub.LSB) of a plurality of user data output by AD converter
14 are replaced with bit data C.sub.1 to C.sub.n+1 of a desired
control signal, by signal synthesizer 16. In this case, the
transmission rate of the control signal is one integral-number-th
of the sampling frequency used for the AD conversion.
[0030] For the application target of the present invention, for
example, radio equipment control and radio equipment provided in a
radio base station apparatus based on a W-CDMA (Wideband Code
Division Multiple Access) system, the data transmission rate is
specified to be about 600 Mbps to 2.5 Gbps in the CPRI. A
transmission rate of about several Mbps to about several tens of
Mbps is normally sufficient for the control signal. Accordingly,
the transmission rate required for the control signal can be
achieved simply by replacing the LSBs of the user data, which have
the smallest information amount in the output signal from AV
converter 14, with bit data C.sub.1 to C.sub.n+1 of the control
signal.
[0031] Signal synthesizer 16 need not replace the LSBs of all the
user data (transmission and reception target data) output by AD
converter 14 with bit data C.sub.1 to C.sub.n+1 of the control
signal. Signal synthesizer 16 has only to replace the LSBs of the
user data with bit data C.sub.1 to C.sub.n+1 of the control signal
at every predetermined period. Receive signals for the radio
equipment are normally mixed with noise. Thus, many of the LSBs of
the user data obtained by subjecting the baseband signal to AD
conversion may be considered to be noise components. Consequently,
even when the LSBs of the user data are replaced with the bit data
of the control signal, adverse effects on the user data are almost
negligible.
[0032] Furthermore, to provide the control signal with randomness,
scrambler 15 generates the pseudo random signal and uses the
generated pseudo random signal to scramble each of bit data C.sub.1
to C.sub.n+1 of the control signal. Signal synthesizer 16 then
inserts scrambled bit data C.sub.1 to C.sub.n+1 of the control
signal into the respective LSBs of the plurality of user data.
[0033] For example, if bit data C.sub.1 to C.sub.n+1 of the control
signal are consecutive 1s or 0s, replacing the LSBs of the user
data with the bit data of the control signal results in having DC
components in a frame composed of the plurality of user data. The
DC components reduce the S/N ratio of the user data. This degrades
the clock extracting capability in the process of extracting a
clock signal from a serial signal; this capability, or the
demodulating capability of demodulator 22 in the radio equipment
control, is required when parallel signal converter 21 in the radio
equipment control converts the serial signal into a parallel
signal.
[0034] The present invention uses the pseudo random signal to
scramble the control signal, thus preventing possible consecutive
1s or 0s. This enables a reduction in DC components, thus
preventing the clock extracting capability or the demodulating
capability described above from being degraded.
[0035] An output signal (frame) from signal synthesizer 16 is
converted into a serial signal by serial signal converter 17. The
serial signal is transmitted to the radio equipment control.
[0036] In the radio equipment control, parallel signal converter 21
receives the serial signal transmitted by the radio equipment.
Parallel signal converter 21 then converts the received serial
signal into a parallel signal to acquire and supply a frame signal
and user data to demodulator 22 and to signal separator 23.
[0037] Demodulator 22 extracts the user data from the output signal
from parallel signal converter 21 and demodulates the user data to
output the data as a demodulation signal. Signal separator 23
extracts the control signal from the LSBs of the user data
contained in the output signal from parallel signal converter 21
and supplies the control signal to descrambler 24. Descrambler 24
uses the same pseudo random signal used by scrambler 15 in the
radio equipment to descramble the control signal supplied by
parallel signal converter 21. Descrambler 24 thus reproduces the
original unscrambled control signal. At this time, descrambler 24
uses the frame signal specified in the CPRI to synchronize the
pseudo random signal for use in the descramble process with the
pseudo random signal used for the scramble process by means of
scrambler 15.
[0038] The present invention replaces the LSBs of the plurality of
transmission and reception target data with the bit data of the
desired control signal for transmission and reception. This enables
the desired control signal to be transmitted and received between
the radio equipment control and the radio equipment without the
need to increase the interface circuit or the interface line or to
increase the transmission rate. This makes it possible to prevent
an increase in the costs of the radio equipment control and the
radio equipment.
[0039] In the above description, by way of example, the LSBs of the
user data (transmission and reception target data) are replaced
with the bit data of the control signal at every predetermined
period. However, for example, user data having the largest
amplitude may be extracted at every predetermined period so that
only the LSB of the user data can be replaced with the bit data of
the control signal. In this case, the LSB of the user data having
the highest S/N ratio is replaced with the bit data of the control
signal. This makes it possible to minimize the adverse effect of
the replacement of the LSB of the user data with the control
signal.
[0040] In the above description, by way of example, the radio
equipment, the transmission device, transmit information to the
radio equipment control, the reception device as specified in the
CPRI. However, if the radio equipment control transmits information
to the radio equipment as specified in the CPRI, effects similar to
those described above can also be obtained provided that the radio
equipment control, the transmission device, includes scrambler 15,
signal synthesizer 16, and serial signal converter 17, and provided
that the radio equipment, the reception device, includes parallel
signal converter 21, signal separator 23, and descrambler 24.
[0041] Moreover, even if the serial signal is transmitted and
received as specified in the OBSAI instead of the CPRI, effects
similar to those described above can also be obtained provided that
the transmission device includes scrambler 15, signal synthesizer
16, and serial signal converter 17, and provided that the reception
device includes parallel signal converter 21, signal separator 23,
and descrambler 24.
* * * * *